U.S. patent number 4,038,962 [Application Number 05/717,642] was granted by the patent office on 1977-08-02 for automatic power controller for a wire saw.
This patent grant is currently assigned to Coggins Industries, Inc.. Invention is credited to Roy Lynnard Tessner.
United States Patent |
4,038,962 |
Tessner |
August 2, 1977 |
Automatic power controller for a wire saw
Abstract
To maintain the cutting wire of a wire saw properly bowed with a
substantially constant cutting pressure on the stone, an automatic
power controller is utilized consisting of a meter with relay
contacts. The meter measures the current flowing to the main power
motor for the wire saw which drives the wire. When this current
falls below a selected value, the meter through the relay means
turns on a slow speed wire saw dolly feed down motor which down
feeds the wire into the stone. This increases wire cutting pressure
and restores wire bow to the optimum degree for efficient and rapid
cutting. The increase in wire pressure and resulting drag increases
current consumption to the main wire saw drive motor. When this
current is increased to its original value, the meter turns off the
slow speed down feed motor for the dolly.
Inventors: |
Tessner; Roy Lynnard (Atlanta,
GA) |
Assignee: |
Coggins Industries, Inc.
(Elberton, GA)
|
Family
ID: |
24882871 |
Appl.
No.: |
05/717,642 |
Filed: |
August 25, 1976 |
Current U.S.
Class: |
125/21 |
Current CPC
Class: |
B23D
57/0061 (20130101); B23Q 35/12 (20130101); B28D
1/08 (20130101) |
Current International
Class: |
B23D
57/00 (20060101); B23Q 35/12 (20060101); B23Q
35/00 (20060101); B28D 1/02 (20060101); B28D
1/08 (20060101); B28D 001/08 () |
Field of
Search: |
;51/165.92,165R
;125/21,12 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Whitehead; Harold D.
Attorney, Agent or Firm: Newton, Hopkins & Ormsby
Claims
I claim:
1. In a wire saw having a support frame, a dolly for transporting a
cutting wire movably mounted on the support frame, a cutting wire
driving motor on the dolly, and a feed down motor means for the
dolly, an automatic power controller comprising:
a current measuring meter electrically coupled with said cutting
wire driving motor to constantly measure the current flowing to
said motor, said current measuring meter including a relay having
an electrical contact coupled with said dolly feed down motor means
and responsive to a decrease in the measured current to the cutting
wire driving motor, resulting from a lessening of a load on the
cutting wire driving motor due to reduced cutting pressure and drag
on the cutting wire for turning on said dolly feed down motor means
until normal cutting pressure and drag is restored to said wire and
the load and current of the cutting wire driving motor are returned
to normal values.
2. The wire saw recited in claim 1, wherein said current measuring
meter is coupled to the cutting wire driving motor through an
induction coil slipped over a power supply lead of the cutting wire
driving motor.
3. The wire saw recited in claim 1, wherein said cutting wire
driving motor and said feed down motor means for the dolly have
different operating voltages, and the coil of said power relay is
electrically coupled to the power supply line of the feed down
motor means and also electrically coupled with the current
measuring meter.
4. The wire saw recited in claim 3, wherein said current measuring
meter includes a plurality of terminals electrically coupled to the
power supply line of said feed down motor means for the dolly.
5. The wire saw recited in claim 1, wherein said power relay
comprises an integral part of said current measuring meter.
6. The wire saw recited in claim 5, wherein said current measuring
meter is an AC ammeter.
7. The wire saw recited in claim 1, wherein said feed down motor
means for the dolly comprises an electric motor operated power
winch including movable suspension cable means connected to and
supporting said dolly for movement.
Description
BACKGROUND OF THE INVENTION
Heretofore, in the art of stone cutting by means of a
power-operated wire saw, no method for automatically controlling
the main saw motor load has been known. The only available means of
control have been mechanical feeds of various types which do not
regulate the motor load. These prior art control devices do not
adjust the sawing for constant horsepower, and therefore yield less
cutting and rougher cutting.
The objective of this invention is to satisfy the need of the prior
art to maintain the load on the main wire saw constant. If this
load is constant, the resulting sawing is improved both in quantity
and quality.
The invention utilizes a commercially available meter controller
having internal switching contacts which are adjustable to close or
open at a setting determined by the position of a meter control
knob. The meter is set to a certain motor current value, usually
ninety percent of the main motor's maximum current. The meter will
then hold this value by down feeding the wire dolly whenever the
motor current falls below the set value due to relaxing of the
bowed cutting section of the wire. When the dolly down feed returns
the proper bow curvature and cutting pressure to the wire, the load
on the main drive motor and the motor current being drawn will
return to the original preset value and the meter through its relay
contacts will turn off the drive of the dolly.
The invention can be utilized on a wide range of saw types such as
single wire strand saws or multiple wire saws. The meter controller
is easily installed by disconnecting one power lead to the main saw
drive motor and slipping a current transformer coil over the lead
and reconnecting it. The meter controller turns on the wire dolly
down feed motor whenever the power used by the wire driving motor
decreases to a value below the preset optimum. The automatic power
controller is simplified, economical, easy to adjust and yields
increased sawing with improved quality.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a side elevation of a wire saw equipped with the
automatic power controller embodying the invention.
FIG. 1B is a fragmentary elevational view of a wire dolly feed down
motor means mounted near one side of the wire saw.
FIG. 2 is a side elevation of the means shown in FIG. 1B taken at
right angles thereto.
FIG. 3 is a schematic view of the automatic power controller
embodying the invention.
FIG. 4 is a schematic view showing the internal circuitry of a
commercial meter controller employed in the invention.
DETAILED DESCRIPTION
Referring to the drawings in detail, wherein like numerals
designate like parts, the numeral 10 designates a wire saw for
cutting a stone slab 11 or the like suitably supported at 12
beneath a bowed cutting portion 13 of a convoluted sawing wire
14.
The wire saw 10 comprises a main frame 15 having side uprights 16
on which a dolly 17 for the sawing wire 14 moves vertically
relative to the stationary stone 11. The dolly has an upper cross
frame member 18 connected with vertical legs 19 having lower and
upper guide rollers 20 and 21 thereon in rolling contact with the
two main frame uprights 16.
Journaled and supported on the dolly 17 are pulley wheels 22 for
the support and guidance of the sawing wire 14 in a conventional
manner. This wire is driven in one direction to saw through the
stone 11 by a main drive motor 23 on dolly frame member 18, and
associated transmission gearing 24 coupled with the shaft 25 of the
adjacent wire driving pulley 22.
Means, not shown in the drawings, delivers a slurry of water and
abrasive material onto the sawing wire and/or stone to abrade the
stone and accelerate the sawing action.
For most efficient and rapid stone cutting, a constant cutting
pressure on the stone 11 must be maintained by the cutting portion
13 of the wire and this pressure causes an optimum bowing of the
wire as shown in FIG. 1 which must be maintained. As the cutting
wire descends through the stone slab 11, its bow curvature tends to
flatten out with a resulting reduction in cutting and cutting
pressure and the dolly 17 must be fed downwardly to restore the
proper degree of bow to the wire portion 13. The diminishing of the
bow curvature of the wire during cutting and the lessening of the
cutting drag on the wire lessens the load on the main wire driving
motor 23 and reduces the amount of current drawn by this motor. The
automatic power control means of the invention, to be described,
functions to maintain a constant load on the main motor 23 and thus
a constant amount of current flowing to the drive motor. To do
this, the control means responds to a reduced load on the motor 23
and a drop in current drawn by this motor to cause down feeding of
the dolly 17 with a resultant restoration of the bow curvature in
wire portion 13 with increased pressure and drag, to thereby
elevate the load on the motor 23 to the normal preset value and to
return its current consumption to normal.
The down feed means for the wire transport dolly 17 is shown in
FIGS. 1B and 2 and comprises a support stand 40 mounted near one
side of the main frame 15. This stand serves to mount a slow speed
dolly down feed motor 38 which is hinged to the stand 40 at 39. The
motor is counterweighted at 41 to maintain active transmission
gearing 42 between the motor 38 and a gear head winch 43, also on
the stand 40, having a pair of drums 44 which turn in unison to pay
out a pair of suspension cables 45 for the dolly 17, these cables
being wrapped oppositely on the drums 44. The cables 45 are trained
over pulleys 46 at the top corners of frame 15 and are attached to
opposite sides of the dolly 17 as shown at 47.
The gear head winch 43 also has an alternate high speed drive 48 on
the stand 40 which comes into play only when a foot pedal 49 is
depressed to pivot the slow speed motor 38 around the axis of hinge
mounting 39 to slacken and deactivate the slow speed drive 42. The
high speed drive is turned on in such cases as for elevating the
dolly 17 rapidly or for lowering it rapidly from an overhead
position toward the stone to be cut. The automatic power controller
of this invention is concerned only with the slow speed dolly feed
down motor 38 and the main drive motor 23 of the wire saw. The
stand 40 also serves to support a housing 50 for the automatic
power controller, now to be described.
Referring to FIG. 3, the main wire saw drive motor 23 and its AC
supply is shown along with the slow speed dolly feed down motor 38
and its AC power supply. A commercially available meter relay unit
51 of a type manufactured and sold by Simpson Instruments, 853
Dundee Ave., Elgin, Ill. 60120, is employed in the invention to
measure the current flowing to the main motor 23 of the wire saw.
When this current falls below a selected value, customarily 90
percent of the motor's maximum rated current, a built-in relay 52
of the meter 51 will turn on the slow speed dolly down feed motor
38 which, through the winch means 43 and 44 and cables 45, will
lower the dolly 17 and restore the optimum degree of bow in the saw
wire portion 13. The resulting increased pressure and drag on the
wire portion 13 will increase the load on the main drive motor 23
and will increase the motor current to the original preset value.
This motor control operation is performed automatically by the
Simpson motor-load meter relay unit or an equivalent control
means.
As the wire 13 cuts downwardly through the stone 11 and loses some
of its bow curvature and its pressure against the stone and drag
are lessened, the load on motor 23 is correspondingly lessened and
the motor current being measured by the meter 51 drops from the
optimum value. It is this drop which activates the control
instrument initially, as described, and causes a substantially
constant load to be maintained on the motor 23 during continuous
operation of the wire saw automatically. The control system is
sufficiently sensitive so that in practice, when the desired
current value to the motor 23 is preset with a control knob on the
instrument 51, the current to the motor 23 and its load will be
maintained nearly constant at all times so that the bow of the wire
portion 13 and its drag and cutting pressure will be nearly
constant, which is the purpose of the invention, to assure the most
efficient and economical cutting or sawing.
A sensor or transformer coil 53 constituting a conventional part of
the meter 51 is slipped over one power lead 54 going to the main
drive motor 23. The coil 53 is not directly or physically in
contact with the lead 54. The coil acts as a transformer in
conjunction with the AC ammeter 51.
A manual on-off switch 55 is provided on the control meter-relay
instrument and the built-in power relay 52 has contact means 56
connected in the power supply line 57 to the 115 volt AC slow speed
dolly feed down motor 38.
FIG. 4 shows the internal circuitry for the described Simpson meter
51 with built-in control relay 52 and since the instrument is
conventional and commercially available, the circuit need not be
described in detail. The instrument terminals A and B connected
with the transformer coil 53 are indicated in both FIGS. 3 and 4.
The built-in relay terminals 14 and 15 in FIG. 4 are also
identified in FIG. 3 as well as the 115 volt power terminals 8 and
9 connected with the meter 51. It is believed that the purpose and
mode of operation of the Simpson meter-relay unit 51-52, as
employed in connection with the two electric motors 23 and 38 of
the wire saw and dolly, may now be fully understood for purposes of
the invention without further description. The automatic power
controller embodied in this instrument constantly measures current
flowing to the main wire saw motor 23 and when the current value
falls below the desired value due to slackening of the wire portion
13, as explained, the slow speed feed down motor 38 for dolly 17 is
turned on automatically. This quickly restores the proper bow and
tension to the wire 13 and the resulting increased load on the
motor 23 returns the current consumption of this motor to the
normal selected value automatically. When the main motor current is
increased to its original value, the meter through its relay 52
turns off the dolly feed down motor 38.
It is to be understood that the form of the invention herewith
shown and described is to be taken as a preferred example of the
same, and that various changes in the shape, size and arrangement
of parts may be resorted to, without departing from the spirit of
the invention or scope of the subjoined claims.
* * * * *